Experts estimate that 65% of people experience shoulder pain at some point in their lives,1 and one common shoulder problem is bursitis. Shoulder bursitis occurs when the large bursa near the top of the shoulder becomes inflamed.
The shoulder’s soft tissue structures—non-bone structures, such as muscles, ligaments, tendons, and bursae—are packed closely together, so their health is interdependent. If one becomes damaged others are likely to follow. Therefore, shoulder bursitis can be the result of other shoulder problems as well as the cause of new problems.
What Is Shoulder Bursitis?
Shoulder bursitis symptoms typically include tenderness at the outer shoulder, especially when raising the arm above the head. A person with shoulder bursitis may find it painful to raise the arm, get dressed, or put pressure on the side of the affected shoulder.
The shoulder’s subacromial bursa is the largest bursa in the body2 and is susceptible to bursitis. It is located below a part of the shoulder blade called the acromion (hence the name “subacromial”). If this bursa becomes inflamed it is called shoulder bursitis or subacromial bursitis.
A diagnosis of shoulder bursitis is often accompanied by a diagnosis of tendinitis or shoulder impingement syndrome. These are separate but often overlapping conditions that affect the soft tissue around the shoulder joint.
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The acromion is the topmost part of the shoulder blade and forms the boney top of the outer shoulder. The acromion hangs above—but does not touch—the bones that form the shoulder’s ball-and-socket joint (glenohumeral joint). Sandwiched between the acromion and shoulder joint are the rotator cuff muscles, which control arm movement, and tendons, which attach muscles to bones.
The subacromial bursa provides a cushion and reduces friction between the shoulder’s muscles and tendons and the acromion.
When a subacromial bursa becomes irritated it may thicken only a tiny amount.2 This small change can cause pain even though swelling may not be evident.
Tendinitis and Shoulder Impingement Syndrome
A tendon is a fibrous tissue that connects muscle to bones. Tendons are flexible but not very elastic, and can become torn or damaged. When a damaged tendon becomes inflamed and swollen it is called tendinitis.
Shoulder impingement syndrome is an umbrella term that describes the painful pinching of soft tissue between the shoulder’s ball-and-socket joint (glenohumeral joint) and acromion. It results from swelling of the soft tissue in the shoulder.
Sometimes swelling from shoulder bursitis or tendinitis can cause shoulder impingement syndrome. Other times shoulder impingement syndrome is caused by another condition, such as acromioclavicular arthritis or rotator cuff tears. When this happens, the impingement can irritate the bursa and tendons, eventually resulting in bursitis or tendinitis. It is estimated that up to 90% of shoulder bursitis cases originate from tears in the rotator cuff muscles.2
Some researchers have suggested doing away with the label “shoulder impingement syndrome” because today’s medical imaging (e.g. ultrasound and MRI) allows for more precise diagnoses.3
Septic Shoulder Bursitis
Septic shoulder bursitis, in which the bursa is infected, is unusual but can be serious. People with septic shoulder bursitis will experience the same symptoms described above and may also feel tired, feverish, and sick, and notice warmth and redness at the shoulder. Anyone with septic shoulder bursitis must seek medical attention to be treated with antibiotics to prevent the spread of infection into the bloodstream.
See Septic Bursitis